1. Field of the Invention
The present invention relates to polycyclic polymers and particularly to photodefinable polymer compositions that include polycyclic polymers.
2. Description of Related Art
The rapid development of the microelectronics industry has created a great demand for photodefinable dielectric polymeric materials with improved electrical characteristics for the packaging of each succeeding generation of microelectronic devices. Trends in the industry require integrated circuits that are smaller, faster, and consume less energy. To meet these demands, integrated circuitry and the packaging of such circuitry must be of higher density with sub-micron feature definitions. One method of increasing the number of components per chip is to decrease the minimum feature size on the chip. Consequently, conducting lines must be made thinner and placed in closer proximity to one another. The reduction in spacing between conducting lines in the circuitry and packaging of such circuitry results in a concomitant increase in the efficiency and speed of the circuit enabling greater storage capacity, faster processing of information, and lower energy requirements. However, the reduction in spacing between conducting lines can cause an increase in capacitive coupling of the lines resulting in greater crosstalk, higher capacitive losses, and an increased RC time constant.
In order to limit any such increase in capacitive coupling and deleterious effects such as propagation delays, simultaneous switching noise and the like, considerable interest in high performance polymers having a low dielectric constant has been shown. In addition, interest in such low dielectric constant materials having an appropriate modulus for use in packaging integrated circuitry has also been shown. However, such here to known polymers can often be difficult to pattern, for example, often the etch properties of such low dielectric constant polymers and photoresist compositions used for patterning them are very similar. Accordingly, efforts to selectively remove portions of the polymer can be problematic. To overcome this selectivity problem, it is known to form an interposing material between the polymer and the resist composition where such interposing material can be selectively patterned to form a hard mask which subsequently can be used in the patterning of the underlying polymer material.
The additional steps required to form a hard mask are not cost effective and hence alternate methods for patterning the low dielectric constant polymer material that do not require such steps would be advantageous. To this effect, U.S. Pat. No. 6,121,340 discloses a negative-working photodefinable dielectric composition comprising a photoinitiator and a polycyclic addition polymer comprising repeating units with pendant hydrolyzable functionalities (e.g., silyl ethers). Upon exposure to a radiation source, the photoinitiator catalyzes the hydrolysis of the hydrolyzable groups to effect selective crosslinking in the polymer backbone to form a pattern. Thus the dielectric material of the '340 patent is in and of itself photodefinable. However, the dielectric compositions disclosed in the '340 patent disadvantageously require the presence of moisture for the hydrolysis reaction to proceed. As known, the presence of such moisture in the dielectric layer can lead to reliability problems in completed devices and device packages.
Therefore, it would be desirable to provide low dielectric constant materials having an appropriate modulus for use in the microelectronic industry that are in and of themselves photodefinable but which do not require the presence of moisture to be photodefined. In addition it would be desirable to provide methods for the use of such photodefinable materials and to provide microelectronic devices that employ such photodefineable materials as dielectric materials.